The long term objective of this research is to understand the interactions between the glycosaminoglycan (GAG)-dependent serine proteinase inhibitor, heparin cofactor II (HCII), GAGs and thrombin and attempt to define how these interactions regulate the cytokine-like effects of thrombin. The first part of the proposal examines the structural features of HCII which specify its functional properties with respect to GAG and thrombin recognition. Proposed hypotheses will be tested by site-directed mutagenesis of recombinant HCII expressed in baculovirus-infected insect cells. The second part of the proposal aims to characterize and identify stromal elements from fibroblasts, smooth muscle cells and their extracellular matrix which accelerate the HCII-thrombin reaction and their modulation by inflammatory cytokines. The final part of the proposal focuses on defining the in vivo extravascular distribution of HCII, ATIII, HCII-binding proteoglycans and thrombin. The outcome of these experiments will provide a clearer understanding of the significance of HCII, thrombin and GAG interactions.